Plastic hypodermic syringe



Nov. 20, 1951 H. w. NELSON PLASTIC HYPODERMIC SYRINGE Filed Oct. 15, 1948 I INVENTOR. HARRY W NELSON AVV'UF/VE'Y Patented Nov. 20, 1951 UNITED STATES PATEN oF-Flce '2,575,425- U v PLASTIC HYPODERMIC. SYRINGE Harry W. Nelson, Arlington, N; J. Application ctober15, 1943, Serial No. 54,600

4Claims. (01.128 218) The subject of this invention is a novel and valuable hypodermic syringe.

The present invention involves my discovery, verified by actual and repeated tests, that a hypodermic syringe having. its cylinder or barrel and also its piston or plunger made of the plastic known as nylon has unique advantages. As is well-known a hypodermic syringe is an instrumentality which is essential to the surgeon and physician, and one of paramount importance in saving life, in defeating pain, in instantaneously effecting anaesthesia in operative emergencies, and, as for injecting streptomycin and the like, in not only hastening the healing of operative wounds but also for preventing fatalities following serious operations.

A hypodermic syringe, it will be appreciated. should have no brittle and frangible parts, and it also should be capable ofsterilization prior to its actual use. Glass syringes have one longrecognized disadvantage. They are fragile and easily broken, making them Wholly unsafe for use after breakage or if cracked; and'ordinarily dangerous to use, because of'the chance of breaking, cracking or chipping during use. Their essential fragility, the lesser of the two just mentioned defects, is, nevertheless, a seriousone from the standpoint of expense; or if the barrel alone breaks, the piston or plunger, usually made to lit a particular barrel, is rendered useless; and if the plunger breaks, the barrel is rendered useless. The idea of making these partsof a material other than glass has been an intriguing oneybut such an idea has long been considered abortive, because of-the prime necessity that the syringe must'be made of some material capable of being boiled for sterilization and otherwise sterilizable. True, it hasbeen found that some plastics can be sterilized byimmersion in alcohol;

but this is inadequate for many uses required of a hypodermic syringe.

It have discovered, as already stated, that all these. difiiculties are fully overcome if the syringe parts having to be sterilized are made of nylon; As. isknown, this material is non-brittle; and what I have demonstrated is that an article made of nylon can be sterilized by the standard procedures of boiling, autoclave steaming and chemical sterilization.

By the present invention there is provided a hypodermic syringe in which all the parts thereof requiring sterilization are made wholly of nylon. 'A simple form of-hypodermic syringe "is one comprising merely-two parts; a cylinder or 2. syringes, an embodiment of the. invention is herein illustrated and described of the two-part kind just described.

"A'featu're'j of the present, invention, further, isashaping of the nylon plunger at its inner or working end' so that thesame there incorporates a special annular flare. or skirt, the tip or working end. of. which may, if desired, but not necessarily, be a.. few .thousandths of. an inch larger in diameter. than the internal diameter of the cylindrical main interior of' the barrel. Sucha flare, with both the barrel and the. plunger made of nylon, gives a result long sought'in the art, which is to obtain the effect of apositive sea1, making the syringe absolutely leak-proof under thepressures. created in use.

Forv further comprehension. of the invention, and of the objects and advantages-thereof, reference will be had to thefollowing description and accompanying drawings. and to. the. appended claims in which the various novel. features of the invention are more particularly set forth.

In the accompanying drawings forming a material part of this disclosure:

Fig. 1. shows the embodiment above mentioned,

in side elevation,v with the plunger sent all the way into the. barrel, and with the latter partially broken away and partially in section; this view being drawn. to about full scale inthe. case of say a. two .0. 0. .capacity. syringe.

Fig. 2 is an. end elevation, looking toward the left, in, Figl .1'.

Fig. 3 shows. the. plunger, drawn to. about twice fullscale, and also, in. axial section, a portionof the barrel. intermediate .its.v ends.

Fig. 4-is, on a scalemuchenlarged over that of Fig. 3, a fragmentary. axial. section taken through theplunger atitsworking end; this view being takenon theline 4.--4' ofFig. .31.

Referring tothe drawing more. in detail,.. the barrelillustrated. is. as; a. whole marked I 0; Said barrel'isshown as asingle, piece of. nylon, which may be molded. to. the. desired shape allover, and which. includes. a main plunger. receiving portion ll cylindrical insid'eand. outside, .a finger-hold" flange l2. elongated, laterally. of. said portion, l I. and atithe fully. open. or rear end of tliebarrel, and anozzle portion, M. Said nozzle of course is hollowfrom-endto end, as indicated.

at |5," with ,this channel'through the nozzle com: munica'ting. at its inner, end with the interior offthe main portion ll ofthebarrel at its inner end. "The,free,,extr.emity ofthe nozzle l4'may be 'bluntas shown, or. rounded, or converged'to, afine needle point, or, if "desired, the outer end portionof the nozzle may be. kept. substantially as shown. or otherwise contoured and. externally threaded for attachment thereto of a removable.

garages in coacting resiliently yieldingly with a specialformation at the inner or working end of the plunger to be explained in a moment and including the flare aforesaid. But by no means is the invention to be limited to a somewhat grayishly milky nylon or any other colored or tinted nylon, as a transparent nylon may well serve or any other plastic having characteristics of nylon as to its ability to withstand repeated sterilization, without distortion, by conventional procedures including those involving substantial temperatures and having the desired degree of resiliency and elasticity.

Referring to the piston or plunger, this, which is as a whole marked 16, is exteriorly cylindrical, and may be of a diameter over the major part of its length either substantially the same as the interior diameter of the main barrel portion H or suitably less than the interior of said main barrel portion so as to have any suitable or desired clearance therefrom. Such major part of the length of the plunger is actually the plunger proper l1, and the plunger comprises said portion l7 and, at the outer end of the tation 20 presented by plunger material is eiitirelypr substantially in correspondence with the convex surface of a segment of a sphere.

While I have illustrated and described the preferred embodiment of my invention, it is to be understood that I do not limit myself to the precise construction herein disclosed and the right is reserved to all changes and modifications coming within the scope of the invention as defined in the appended claims.

Having thus described my invention, what I claim as new, and desire to secure by United States Letters Patent is:

plunger, a centralized annular flange, prefer- I ably of less diameter than the maximum facewise dimension of the finger-hold flange i2 on the barrel [0, for providing an integral thumb-thrust button 18. i I I At the working end of the plunger is the aforesaid slight special flare or skirt, as may be noted in Fig. 3, but which is clearly shown in Fig. 4. and there marked l9. There is some lateral flexibility or elasticity of said flare due to the nature of the nylon, with the parts relatively dimensioned as indicated; and for coacting with this flexibility an additionally advantageous fea-. ture may be the flexibility of the side wall of the main barrel portion ll due to its desirable extent of exceptional thinness, as a thickness for said wall of the order of about one-twelfth of the external diameter of the said main barrel portion ll preferably is provided.

An additional advantageous feature, to constitute the flare or skirt 19 in a manner to augment its sealing eflicacy, is a cavitation such as time to make this crest self-sustaining by a gradual increase in the thickness of said flare or skirt in a direction away from its crest, as indicated at 2i. In other words, because of the thin or relatively sharp, knife-like free edge or crest of I the fiare or skirt 19, said edge or crest has tightsealing substantially line contact with the inner surface of the barrel [0, particularly since the flare or skirt I9 is more or less elastic and is more or less expanded under the pressure developed in the barrel [0 by movement of the plunger l6 against a body of liquid contained in said barrel during normal use of the syringe. For maximum eiiiciency of the cavitation 20 in the regard just noted, the cavitation ,is desirably made so that all cross-sections taken thereof axially of the plunger IE will define substantially the shape shown in Figs. 3 and 4.

i It will be observed that the surface of the cavi l. A hypodermic syringe comprising a barrel. a plunger slidable in said barrel, and an annular outwardly and forwardly flaring skirt integral with said plunger adjacent the distal end thereof, said skirt having substantially annular line contact at its inner or free edge with the inner surface of said barrel and being spaced throughout the remainder of its length from the inner surface of said barrel, said skirt being sufliciently elastic at its inner or free end portion to be urged radially outwardly into tight sealing annular substantially line contact with the inner surface of said barrel under the pressure developed by movement of said plunger in said barrel against a body of liquid contained therein in the normal use of the syringe and to yield radially inwardly only on the entry of said plunger into said barrel.

2. A hypodermic syringe as set forth in claim 1 in jwhich the skirt tapers in cross section toward its inner or free end to an extent suflicient to ensure elasticity only at said free end.

3. A hypodermic syringe plunger for use with a} hypodermic syringe barrel of predetermined inside diameter, said plunger including a main part and an integral annular outwardly and forwardly flaring skirt adjacent its distal end, said skirt tapering in thickness towards its inner or free end, said end of said skirt being dimensioned to establish a substantially annular line contact seal with the barrel when inserted therein and being sufficiently elastic to be urged outwardly under the pressure developed by movement of said plunger into said barrel against a body of liquid contained therein, as in the normal use of a hypodermic syringe, without appreciably increasing the area of contact between said skirt and said plunger and to yield radially inwardly only when inserted into said barrel.

4. The hypodermic syringe plunger of claim 3 in which the main part and the skirt thereof are of nylon and the skirt has an unbroken surface skin.

HARRY W. NELSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 201,628 Peters Mar. 26, 1878 514,378 Neal Feb. 6,1894 781,283 Higgins Jan. 31, 1905 1,557,837 Hein Oct. 20, 1928 1,860,898 Meyer May 31, 1932 1,948,982 Cutter Feb. 27, 1934 2,345,302 Smith Mar. 28, 1944 2,419,401 Hinds Apr. 22, 1947 FOREIGN PATENTS Number Country Date 632,883 Germany July 15, 1936 

